1. Field of the Invention
The invention relates to a device for detecting incident laser radiation and determining the intensity of the radiation. More particularly, the present invention relates to a device using polyconducting film to detect incident laser radiation, to compensate for ambient temperature fluctuations, and to provide self-protection against high intensity radiation by changing phase dependent upon the incident radiation intensity level.
2. Description of Prior Art
Optical radiation detectors may be broadly divided into two main categories: thermal detectors and photon detectors. Photon detectors are more sensitive and include photomultipliers, photoconductors, photodiodes and avalanche photodiodes. Thermal detectors are less common but have the advantage of larger bandwidth and do not require cooling. Such detectors are effective for detection but have a response time too slow to provide effective or self-protection when exposed to high intensity laser beams.
Thermal detectors operate on the principle that the heating effect of the incident radiation causes a change in some electrical property of the detector, e.g. resistance, and thus the theoretical response is proportional to the energy absorbed and is practically the same over a wide range of the wavelength, especially in the infrared portion of the spectrum. The time constant is generally a few milliseconds and hence these detectors are rarely used where fast response times and high data rates are required.
Photon detectors operate on the principle that there is a direct interaction between the incident photons and the electrons of the detector material and thus that the detector response is proportional to the number of photons absorbed. These detectors usually have sensitivity one or two orders of magnitude greater than thermal detectors and time constants of generally a few microseconds. However, their spectral response varies with wavelength and the majority require cooling. The present invention is a device for detecting laser radiation and measuring laser power that is applicable to a wide variety of lasers and has very short response times permitting real-time detection and self-protection against heat degradation by high intensity lasers not possible by conventional thermal detectors.